The Formula DAC is the first in the aqua’s production to show a proprietary D/A conversion system, that we name Optologic. The signals sent to the resistor ladders are generated by a proprietary digital circuit, implemented inside an FPGA (Field Programmable Gate Array). Formula has a sign-magnitude converter structure, and this requires not two but four 24 bit resistors banks, each one made of very low tolerance discrete resistors. Aqua believes that the more musical D/A conversion system is based on the circuit usually identified as "resistor ladder." This technology has been substituted in the mass-market by the so-called sigma-delta converters. The sigma-delta converter is a near-completely digital circuit and for this reason it can be can be integrated on silicon and produced at low-cost. A quality resistor ladder DAC instead uses a circuit based on a set of high
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